In the past, it has been known to fabricate weed trimmers or whackers using belt drives to which a number of cutting blades are attached. The blades rapidly cut grass and weeds as the blades are caused to spin about a moving belt that is stretched between two pulleys. These types of belt drives are shown in U.S. Pat. Nos. 3,699,757, issued to Hulburt on Oct. 24, 1972, for BELT CARRIED CUTTERS AND MOUNTING MEANS THEREFORE; 4,164,835, issued to Conte on Aug. 21, 1979, for GRASS CUTTER; and 3,831,358, issued to Marsh et al on Aug. 27, 1974, for BELT AND CONNECTING MEANS THEREFOR.
One of the problems with blade carrying belt drives is their tendency to throw or damage the drive belt, when the moving blades encounter rigid obstacles. U.S. Pat. No. 3,699,757 teaches that it is useful to pivotally mount the blades to the belt, so that they can deflect when they encounter an obstacle. The deflecting blades are designed to prevent belt damage and dislodgement of the belt from the pulleys.
It has been determined, however, that pivoting blades have several drawbacks. In the first instance, the blades require a complex shape, so the pivotable mounting adds cost and complexity. In the second instance, pivoting blades often fail to cut through dense brush and weeds that are generally thicker than average, because of the adjusted cutting angle.
The current invention seeks to provide a blade cutting belt drive system that has none of the above drawbacks.
The belt drive of the present invention has rigidly mounted blades that are secured to the belt by a set screw. The set screw allows for ease of removal of a damaged blade and quick replacement of a new blade.
The belt drive of the current invention features blades that are sharpened on both front and back edges. The purpose of having dual sharpened edges is to allow a worn bladed belt to be reversed to provide a sharp bladed belt. In this manner, the belt of the invention lasts approximately twice as long as does a conventional belt.
In order to prevent the belt from being torn off, or dislodged from the pulleys, the present invention uses a timing, or V-shaped belt. The V-shape creates a more positive belt engagement and prevents the belt from being dislodged or from slipping off of the pulleys. Timing belts act as gears, whose teeth engage the mating teeth of the pulley drives. The positive engagement of the timing belt about the pulleys prevents the belt from being torn therefrom.
The inventive weed trimmer also features a simple adjustment for tensioning the belt about the pulleys. The shaft of the forwardly mounted pulley is rotatably anchored to the frame by a machine screw, which is tightened in place by a collar nut. The machine screw rides within a slot of the weed trimmer frame, so that the rotatable pulley can be pulled forward to adjust the belt tension, and then fixedly secured in place with respect to the frame.
The weed trimmer of this invention also comprises a cutting blade on a nose portion, which cutting blade can sever grass or weeds that lie close to a wall or other structure, or which cannot be reached by the cutting blades of the belt. The nose portion is angled for directing grass, close to the aforementioned wall or structure, into the cutting blades of the belt.
A cowling is provided that has an outwardly flowing surface for directing clippings away from the operator.